Deafness in Adults

See related articles deafness and congenital deafness.

The normal hearing range is 0-20 decibels (dB), where 0dB is the threshold for the perception of sound at a given frequency for people with normal hearing.¹ Deafness is a partial or complete loss of hearing, also known as hearing impairment. Hearing loss is measured in decibels hearing loss (dB HL). It can be graded as follows:²

• 20-40dB HL: mild, cannot hear whispers
• 41-70dB HL: moderate, cannot hear conversational speech
• 71-95dB HL: severe, cannot hear shouting
• >95dB HL: profound, cannot hear sounds that would be painful for a hearing person to listen to.

There are two types of deafness and patients may present with one or both of these:
Conductive hearing loss - this occurs when there is a problem in the transmission of sound waves from the external ear, through the middle ear. The disease processes can occur at any level along this part of the ear.
Sensorineural hearing loss - this refers to problems occurring in the cochlea (most common site of disease), cochlear nerve, or brain stem resulting in abnormal or absent neurosensory impulses. Sensorineural problems are more common in adults.

• There are almost 9 million deaf or hard of hearing adults in the UK, 688,000 of which have severe to profound deafness.
• 21.6% of over 50 year olds and 71.1% of over 70 year olds have some degree of presbycusis (age-related hearing loss). In 0.6% of over 50 year olds and 1.3% of over 70 year olds, this leads to profound hearing loss.
• Deafness occurs slightly more commonly in males than in females and is thought to be more likely to occur in caucasian people.⁴
• There is less data available regarding incidence of hearing impairment but this is estimated to be about 1% per year of 45-55 year olds and a 1.5% per year in over 55 year olds.⁵
• 2 million people wear hearing aids but it is thought that twice as many could benefit from hearing aids.

History^1,6

Presentation may be with sudden or gradual, unilateral or bilateral hearing loss, depending on the aetiology. A history should be taken as with any other problem.

Risk Factors

• The main risk factors for adult hearing impairment is age and excessive noise exposure.
• There are certain risk factors contributing to specific types of deafness (see aetiology below) such as previous ear infections, trauma, viral illness and so on.
• There is more limited evidence suggesting that a positive family history, elevated lipid levels, smoking, pale eye colour and caucasian race are also linked with development of hearing impairment.⁷

Physical examination - this should include inspection of the external ear (note minor disfigurements as the development of the different components of the canal is closely related), and examination of the tympanic membrane, looking for obstructions (cerumen, foreign bodies), evidence of infection, perforation, tympanosclerosis, cholesteatoma or effusion.
Functional examination - the whispered voice test and tuning fork tests (Rinne's and Weber's tests) can be carried out simply and effectively but ultimately, if these reveal hearing impairments, patients need to be referred on for audiometric testing which will enable precise quantification of the degree of hearing loss and help identify the site of pathology. See article on the overview of deafness for more detail on how to perform whispered voice test and tuning fork tests.

There many causes of congenital of deafness (which may or may not be part of a syndrome) and these persist into adulthood. These are covered in our article on congenital deafness. Acquired causes are outlined below.

Conductive hearing loss

Occlusion

• Nature - occlusion may occur as a result of cerumen (notorious for getting impacted with the use of cotton-tipped buds), foreign body impaction (more often occurring in the young child and in patients with mental health problems), oedema (if severe, this may limit the action of the ossicles) or exostosis (benign bony growth in the external auditory canal sometimes precipitated by frequent cold water swimming).
• Presentation - this may be a unilateral (e.g. foreign body) or bilateral painless loss of hearing (unless there is impaction and associated infection of the foreign body) which is usually sudden as the canal finally occludes.
• Management - if there is no history of otitis media, tympanic perforation or inner ear surgery, cerumen can be safely irrigated out with body-temperature warm water; it may need to be softened first with several days application of vegetable - particularly olive - oil. If you have a good view with the otoscope, it is possible to curette it out. If the patient is co-operative, non-impacted foreign bodies can be irrigated or removed in the same manner as for cerumen. If in doubt, refer to the ENT team. Oedema needs to have its underlying cause treated. Large exostoses can lead to impairment of normal cerumen migration - surgical removal is only indicated if they are symptomatic.
• Prognosis - this is good for these conditions and normal hearing should be restored in the absence of complications or underlying disease.

• Nature - there are different types of infection that concern the outer and middle ear but the principle conditions are otitis externa (most commonly caused by Pseudomonas aeruginosa and Staphylococcus aureus), otitis media (which can cause middle ear effusions that decrease the mobility of the tympanic membrane and the ossicular chain) and less commonly with regards to hearing loss, sinusitis which can cause a temporary hearing loss if there is associated swelling of the eustachian tube.
• Presentation - otitis presents with a sudden painful loss of hearing. A narrow auditory canal with debris suggests otitis externa and a normal lumen canal with a red, immobile tympanic membrane suggests otitis media.
• Management - this involves removal of any debris and application of local antibiotic drops (possibly applied to a wick which sits in the ear canal if there is severe otitis externa). Systemic antibiotics are only recommended in severe cases. Severe ro recurring cases of otitis media may lead to middle ear effusions. Refer patients with chronic otitis media (see referral criteria below).
• Prognosis - recovery is generally good but chronic otitis media may lead to middle ear effusion or tympanic membrane perforation.

• Nature - this can arise as a result of chronic otitis, trauma (including barotrauma, water accidents, explosions, penetrating injuries or temporal bone fracture) and from surgery (e.g. radical mastoidectomy).
• Presentation - the history may be suggestive, coupled with (ususally) painful hearing loss and tympanic membrane perforation on examination of the ear.
• Management - small perforations (<2mm) often heal spontaneously with topical antibiotic cover and instructions to keep the ear dry. If visibility is poor or there is suspicion of more extensive injury, refer to the ENT team.
• Prognosis - this depends on the extent of the perforation and causative factor. Recovery should be complete in the absence of complicating factors.

• Nature - benign cysts, benign and malignant tumours (fibromas, papillomas, adenomas, sarcomas, carcinomas and melanomas) and neurofibromatosis type 2 can all cause tumours within the ear canal leading to conductive hearing loss.
• Presentation - they tend to be associated with gradual, painless, unilateral hearing loss (acoustic neurofibromas tend to be bilateral).
• Management - refer promptly for biopsy ± imaging. If a malignant tumour is confirmed, treatment will include invasive surgery ± radiation therapy.
• Prognosis - depending on the nature of the growth, this ranges from excellent (e.g. benign papilloma) to very poor (e.g. carcinoma of the bony ear canal involving the tympanic membrane have a 5-year survival rate of <25%⁵).

• Cholesteatoma - this is a 3-dimensional collection of epidermal and connective tissues within the middle ear. Patients characteristically present with chronic, suppurative otitis media and a progressive deafness. The tympanic membrane may be seen to be retracted or perforated with an epithelial lining to it. The cholesteatoma grows independently and can be locally invasive and destructive: if you suspect this, refer the patient for surgery.
• Adenoids - occasionally, rather than regressing (this usually occurs at about 5 years of age), these carry on growing to eventually block off the Eustachian tube, so causing a painless, bilateral hearing loss in young adults. Refer for surgery.
• Otosclerosis (otospongiosis) - this is where there is abnormal bone deposition at the base of stapes so preventing normal ossicular vibration. Typical patients are middle-aged white women who present with painless, progressive, bilateral hearing loss and a positive family history of this condition. Many manage with hearing aids alone but some need to be referred on for surgery.
• Myringosclerosis - this is characterised by the deposition of irregular, white, calcium patches on the tympanic membrane. It is not generally problematic when isolated but if it extends to cover associated structures (tympanic membrane, ossicular chain and middle ear mucosa) - tympanosclerosis - significant hearing impairment can ensue. Refer for confirmation of diagnosis.
• Temporomandibular joint syndrome - patients suffer from pain in the jaw, face, and head, especially around the ears; clicking or popping in the jaw and ears; "locking" of the jaws, and pain in opening the mouth. It may be associated with bilateral hearing loss, thought to be due to muscular spasms of the muscles of the inner ear. This is usually a self-limiting condition but a short course of NSAIDs is sometimes helpful.

Sensorineural hearing loss

Bilateral

Presbyacusis (age-induced hearing loss)⁵

• Nature - this is a progressive, bilateral and usually symmetrical loss of cochlea hair cells and degeneration in the cochlea nerve resulting in hearing loss. It initially affects frequencies >2kHz but lower frequencies are involved as it progresses. It is a diagnosis of exclusion.
• Presentation - patients are typically over 50 years old and complain of a gradual deterioration of hearing, experiencing particular problems in understanding speech which becomes muffled (the worst environment is in a crowded room). There may be a history of noise exposure and smoking.
• Management - patients benefit from referral for fitting of a hearing aid and may need adjunctive tools to help them in their daily life.
• Prognosis - this is a progressive condition, the speed of which varies from patient to patient but ultimately, hearing will never improve.

• Nature - exposure to excessive sounds (acoustic trauma) produces a temporary shift in the stimulus threshold of the outer hair cells within the inner ear, so allowing them to recover. Sufficiently intense and repeated exposure results in a permanent threshold shift. Occupational hearing loss is the principle culprit but any noise including military, social and firework noises can all be implicated. High frequencies (typically 4kHz) are the first to be affected, followed by progressively lower frequencies.
• Presentation - usually gradual hearing loss (unless exposure was to a sudden noise such as an explosion) associated with tinnitus in 60% of cases. The problem is bilateral, ± symmetrical and examination of the tympanic membrane is normal.
• Management - if hearing does not recover within a few days of sudden noise exposure, refer for audiometric testing. Patients complaining of occupational NIHL need referral as there may be legal implications.
• Prognosis - if the exposure was moderate (such as at a loud pop concert), recovery may be complete. Prolonged or excessive exposure results in permanent damage. This is not progressive however, and any further hearing loss after exposure ceases is not due to NIHL (it often due to overlying presbyacusis).

• Nature - there are several classes of drugs that are known to consistently damage the inner ear. These include aminoglycosides, cis-platinum, salicylates, quinine and some loop diuretics. Macrolide antibiotics can cause hearing loss and glycopeptide antibiotics can also affect balance. More details of which drugs are ototoxic and their safe dosage levels can be found in the Further Reading.
• Presentation - tinnitus, hearing loss and balance problems may occur following administration of these drugs. The feeling of pressure within the ears is also a common complaint. The symptoms are often insidious and may occur weeks to months after use of these drugs.
• Management - avoid prescription of these drugs in pregnancy, consider lowest dose and check co-morbidity (such as renal function) before prescribing. Symptoms are not reliable signs but should they occur, review the drug regime, considering alternative doses and alternative drugs. If the offending agent has already been stopped, refer for audiometry; these patients may need some supportive measures such as fitting of a hearing aid.
• Prognosis - these patients are often left with long-term hearing impairments but in patients with associated balance disturbances, all but the most severe of cases improve due to central compensation (although the elderly may continue to be unsteady for the rest of their lives).

• Nature - this is being increasingly diagnosed in the context of auto-immune disease (where the diagnosis is confirmed by improvement with the administration of steroids) and in HIV where it may be associated with cytomegalovirus infection (see below).
• Presentation - autoimmune hearing loss presents with rapidly progressing, possibly fluctuating, bilateral hearing loss or attacks of hearing loss and tinnitus resembling Meniere's disease. About 50% of patients also complain of dizziness.
• Management - these patients respond to oral prednisolone. In some patients, low-dose methotrexate may be an alternative to long-term steroids.
• Prognosis - patients should fully recover between episodes but these are recurring.

• Nature - this is a benign tumor arising from Schwann cells of the vestibular division of the eighth cranial nerve within the internal auditory canal or at the cerebellopontine angle. They may occur bilaterally in patients with neurofibromatosis.
• Presentation - occipital pain on the side of the tumour and gradual, unilateral hearing loss (10-22% of patients). There may be vertigo and tinnitus but this is less common. Occasionally there is associated V, VII, IX, X and XI cranial nerve damage and if the tumour is large, there may be compressive effects too.
• Management - refer for MRI imaging with gadolinium. These patients ultimately need to be under the care of the neurosurgeons.
• Prognosis - the tumour itself may be completely excised but in the process, there may be damage to the facial and auditory nerves.

• Nature - this is a condition of the inner ear. Its exact aetiology is unclear but it is thought that increased fluid pressure within the inner ear may be part of the problem.
• Presentation - there are paroxysmal attacks of vertigo associated with vomiting, tinnitus and deafness. These attacks occur at any time and without warning. Deafness is unilateral and initially affects higher frequencies but subsequent attacks involve successively decreasing frequencies.
• Management - after ruling out other pathology with imaging, these patients are managed on low-salt diets ± diuretics. Sometimes, gentamicin is used in the control of vertigo (acting as a chemical labyrinthectomy).
• Prognosis - there may be clusters of attacks interspersed with long periods of well being. Symptoms during attacks may worsen but remission is generally complete but if these are numerous, there may be an eventual long-standing feeling of unsteadiness.

• Nature - this is a sudden sensorineural hearing loss of 30dB within three days which may be associated with tinnitus, vertigo, and aural fullness. Its aetiology is not well known but it may be associated with viral infection or vascular insults.
• Presentation - hearing loss as above and there may be a history of upper respiratory tract infection in the last month.
• Management - refer urgently as these patients need to be started on oral steroids within 3 weeks of onset.
• Prognosis - best for those with minimal hearing loss, no vestibular symptoms and early treatment.

• Nature - this is an abnormal connection between the perilymphatic space of the inner ear and the middle ear cavity. It may be congenital or acquired (such as with barotrauma or straining - lifting, coughing, sneezing).
• Presentation - there is a sudden, unilateral hearing loss associated with vertigo and tinnitus. The history may be suggestive.
• Management - three to six weeks of bedrest. If symptoms do not improve, surgery may be recommended.
• Prognosis - this is variable, depending on the cause and size of the leak.

• Inflammation ± infection (such as encephalitis, meningitis, labyrinthitis, Scarlet fever, typhoid, varicella zoster, otitis interna)
• Trauma (temporal bone fractures)
• Pyrexia
• Auditory neuritis
• Diabetes
• Multiple sclerosis
• Muscular dystrophies
• Paget's disease
• Charcot-Marie-Tooth disease.

Functional hearing loss⁸

• Nature - this is deafness that results from psychological or emotional factors, rather than from physical causes. Diagnosis is sometimes complicated by the presence of a real physical hearing loss, either "overlaid" by the functional loss or in one ear while the other ear has the functional loss (unilateral functional deafness).
• Presentation - this may be in many forms. Look for inconsistencies in responses to tuning fork tests. A quiet question in history taking whilst turning away or moving round the back of the patient may reveal a better hearing than described.
• Management - ultimately, diagnosis can only be confirmed on formal audiometric testing. These patients need to be managed sensitively. An emphasis on how very difficult emotional difficulties can result in very real impressions of hearing loss is helpful.
• Prognosis - this depends on the outcome of the underlying psychological problems.

Referral⁶

The following situations would prompt referral to the audiometry department or an ENT clinic:

• Patients presenting with asymmetric sensorineural hearing loss.
• Patients who need further evaluation of their hearing impairment via audiometric testing.
• Patients who cannot manage without hearing aid.
• Patients with recurrent acute otitis media (more than three episodes in six months or four episodes in one year), chronic middle ear effusions (more than three months in duration), or significant hearing impairment (greater than 30 dB along with an effusion) should be referred to consider the possibility of surgical drainage using myringotomy tubes.
• Tympanic membrane perforations that are > than 2mm, where a full view of the problem is not possible, where associated injury is suspected or in patients where the perforation or hearing loss lasts more than 2 months.
• Suspicion of a tumour either in the external auditory canal or more central tumours such as an acoustic neuroma.

Management options

This depends on the aetiology of the disease process. Underlying treatable causes should be addressed but patients who go on to develop a long term hearing problem have several options open to them:

• Externally worn hearing aids
• Implantable hearing aids
• Additional hearing aids
• Support groups.

Each of these is more fully discussed in our related article on deafness.

The general complications of deafness may be physical or psychosocial. These are discussed in the article giving an overview of deafness.

This depends on the aetiology as outlined above.

This depends on the underlying cause: noise trauma is the most common preventable cause of sensorineural hearing loss. Screening (particularly of the elderly population) has been advocated in order to optimise early intervention and minimize the consequences of hearing loss,⁹ but this is not currently routine practice in the UK. Where there is no known treatment to restore hearing, efforts should be concentrated in maximising what hearing there is left and limiting the psychosocial impact through access to patient support groups (of which there are many, some listed below in the Further Reading) where there is a wealth of information available on social network, practical support tips and information about patient rights.